Known monolithically integrated output stages are used to detect a load current threshold. whereby a switching signal is supplied by a switching logic unit over an output transistor on reaching a set load current threshold. Such output stages are used, for example, in electronic ignition control devices for motor vehicles.
German Published Patent Application No. 43 33 359 A1 describes such a monolithically integrated output stage. However, a disadvantage of the output stage described in German Published Patent Application No. 43 33 359 A1 is that the collector of the switching transistor of the output stage is pulled to an inverse voltage of &lt;0 volt when inductive loads are switched, so that the output transistor of the switching logic can be notched up (i.e becomes unblocked). This occurs despite the fact that the threshold of the load current to be detected has not been reached. This leads to corruption of the signal.
To keep the output transistor blocked even when the collector voltage drops below 0 volt, German Patent Application No. 43 33 359 A1 proposes that a malfunction of the switching logic in inverse operation of the output stage be achieved over a potential-limiting diode and an additional transistor. The output transistor is wired here as a pull-down transistor, so that the interference signals can only be removed at a considerable expense.